The present invention relates to end effectors of an automated equipment used in manufacturing lines, and more particularly to a method and apparatus for automatically realigning the end effector of the automated equipment after undesired contact of the end effector, to prevent a crash of the end effector.
The present invention will be described for a gripper, within an automated handler which palletizes and/or depalletizes parts within a manufacturing line, as an example end effector of an automated equipment used in a manufacturing line. However, as would be apparent to one of ordinary skill in the art from the description herein, the present invention may be used for any other type of automated end effectors such as cutting or grinding tools, welding guns, or other type of automated pneumatic or servo-driven parts within any type of automated equipment that requires proper alignment of the end effector.
Referring to FIG. 1, an automated handler 100 is used in a manufacturing line for assembling an article of manufacture. The automated handler 100 includes a gripper 106 which is an example of an automated end effector within an automated equipment used in a manufacturing line. The automated handler 100 includes a base 102, a movable arm 104, and the gripper 106. The position of the gripper 106 of the automated handler 100 is adjusted via the movable arm 104 such that the gripper 106 may reach down and grip a part 108 for picking up the part 108 to be incorporated in the article of manufacture.
A pallet 110 holds a plurality of parts 108, 112, and 114. Referring to FIG. 2, a top view of the pallet 110 shows a plurality of cells 202, 204, 206, 208, 210, 212, 214, 216, and 218. Typically, each of the plurality of cells holds a corresponding one of a plurality of parts. The pallet 110 is used to transfer the plurality of parts through the manufacturing line during a manufacturing process. For example, the plurality of parts may be automotive parts within an assembly line during manufacture of automotive systems.
The gripper 106 may reach down and grip a part from the pallet 110 for picking up the part to be incorporated in the article of manufacture. Alternatively, the gripper 106 may reach down to place a part into the pallet 110 to transfer parts from a manufacturing line into the pallet 110.
In either case, referring to FIG. 3, the automated handler 100 may not be properly aligned with the cells of the pallet 110. For example, some manufacturing processes heat the plurality of parts within the pallet 110 to high temperatures such as 500xc2x0 C. In addition, the pallet 110 is reused for heating and cooling of a large number of parts. With such repeated heating and cooling of the pallet 110, the pallet 110 warps in shape with time such that the gripper 106 is no longer properly aligned with the cells of the pallet 110.
In any case, when the gripper 106 is not properly aligned with the cells of the pallet 110, the gripper 106 collides with a part within the pallet 110 or any other part of the pallet 100 to result in an undesirable crash. In the prior art automated handler system, the crash of the gripper 106 into a part is detected. Upon detection of the crash in the prior art, the mechanism for holding the gripper from the automated handler 100 is loosened to minimize the stress of force applied on the part and on the gripper from the crash. For example, an air chamber of the prior art holding the gripper 106 is depressurized upon detection of a crash to minimize the stress of force applied on the part and on the gripper from the crash. In addition, an operator is then notified of the crash.
Unfortunately, the automated handler 100 of the prior art is manually reset after a crash. The position of the gripper 106 is manually readjusted to be properly aligned with respect to the position of a part within the pallet 110 to be picked up. The components on the automated handler 100 of the prior art are also manually reset to begin operation of the automated handler 100 again after a crash. However, such manual resetting of the automated handler 100 after a crash results in a relatively long down-time and high labor costs during the manufacturing process.
Thus, a mechanism for preventing an undesired crash of an end effector such as the automated handler 100 is desired
Accordingly, the present invention is an apparatus and method for automatically realigning an end effector of an automated equipment after an undesired contact of the end effector to prevent a crash of the end effector.
Generally, the present invention includes a plurality of contact detectors, and each of the contact detectors are disposed at a respective location with respect to the end effector. In addition, each of the contact detectors generates a respective signal for indicating direction of force on the end effector that results from the undesired contact. Furthermore, the present invention includes an end effector controller that is coupled to the plurality of contact detectors and to the end effector. The end effector controller causes the end effector to move to a reset position after the undesired contact when any of the respective signals from the plurality of contact detectors is greater than a first predetermined level. The reset position includes a respective positional off-set that corresponds to the direction of the force on the end effector that results from the undesired contact as indicated by which of the respective signals from the plurality of contact detectors is greater than the first predetermined level.
In another aspect of the present invention, the end effector controller ignores the respective signals from the plurality of contact detectors when each of the respective signals from the plurality of contact detectors is less than the first predetermined level. Thus, the present invention allows for some light contact by the end effector within a compliancy range. Alternatively, the end effector controller shuts down any driving mechanism of the end effector and notifies an operator of the undesired contact when any of the respective signals from the plurality of contact detectors is greater than a second predetermined level that is typically significantly higher than the first predetermined level. Thus, the present invention prevents damage to the end effector and any part with which the end effector has made contact in the case of a more drastic undesired contact with higher force.
In a further aspect of the present invention, the present invention further includes a carrier for holding the end effector. The carrier allows movement of the end effector along the direction of the force on the end effector that results from the undesired contact. In that case, each of the plurality of contact detectors generates a respective signal indicating the direction of the force on the end effector from the direction of the movement of the end effector during the undesired contact.
The present invention may be used to particular advantage when the carrier includes a hinge joint between the end effector and the carrier for allowing rotational movement of the gripper along the direction of the force on the end effector that results from the undesired contact. In that case, the plurality of contact detectors may also include a plurality of pneumatic cylinders with each pneumatic cylinder being disposed on a respective location on the carrier to retract when a respective direction of the force is applied on the end effector as a result of the undesired contact.
Alternatively, the present invention may be used to particular advantage when the carrier includes a compressed air spring disposed on the end effector for movement of the end effector along the direction of the force on the end effector that results from the undesired contact by deformation of the compressed air spring. In that case, a location of deformation of the compressed air spring indicates the direction of the force on the end effector that results from the undesired contact.
In another embodiment of the present invention, each of at least one contact detector generates a respective signal for detecting the undesired contact of the end effector. The end effector controller causes the end effector to move to a first reset position after a first undesired contact of the end effector when any respective signal from the at least one contact detector is greater than a first predetermined level with the first reset position including a first predetermined positional off-set. In addition, the end effector controller causes the end effector to move to a second reset position after a second contact of the end effector when any respective signal from the at least one contact detector is greater than the first predetermined level after the end effector has been moved to the first reset position. The second reset position includes a second predetermined positional off-set that is opposite in direction from the first predetermined positional off-set and that is twice in magnitude of the first predetermined positional off-set.
In this manner, the end effector such as the automated handler 100 is automatically realigned to a reset position after an undesired contact of the end effector is detected such that a crash of the end effector is prevented. Thus, the high labor costs and large down time associated with the prior art end effectors are effectively reduced with the present invention.